1. Field of the Invention
The present invention relates to communication navigation systems and methods, etc. for performing navigation by transmitting map data to navigation terminals via a communication network. More particularly, the invention is directed to a communication navigation system and method, etc. which can present the latest information with navigation terminals.
2. Description of Related Art
Various types of navigation systems have been proposed, which perform navigation by transmitting map data stored in a server and route guidance information, via computer and mobile communications networks including the Internet, to various types of navigation terminals, such as in-vehicle navigation units, portable navigation units, PDAs (Personal Digital Assistants) and cellular telephones, according to their request. Each of these navigation terminals presents a user with predetermined information visibly and audibly, based on position data detected by a GPS (Global Positioning System) receiver mounted thereon as well as map data transmitted from the server, to guide the user to his or her destination.
In the above communication navigation systems, the server, receiving a request for guidance to a destination from a navigation terminal disposed on a vehicle, calculates the best route, etc. for a total route from a starting point to the destination, and transmits to the navigation terminal the calculated data, etc. en bloc.
However, when the vehicle is heading for a remote destination, and thus needs guidance for a long-distance route, a memory of the navigation terminal may, in some cases, be too small to receive all the calculated data, etc. transmitted from the server. In such cases, the navigation terminal cannot receive new data any longer, and hence cannot update the best route, etc. according to the latest traffic information, etc.